The function cubicnl in the Faust software distribution (file
effect.lib) implements cubic nonlinearitydistortion
[456]. The Faust programming example
cubic_distortion.dsp provides a real-time demo with
adjustable parameters, including an offset for bringing in even
harmonics. The free, open-sourceguitarix application (for
Linux platforms) uses this type of distortion effect along with many
other guitar effects.